POSITIVE MATERIAL IDENTIFICATION (X-Ray Fluorescence)

The object of this nondestructive testing method (also known as PMI) is to identify metal alloys in place using a portable X-Ray fluorescent analyzer that determines the elemental composition of the material.

This test method can be performed on all ferrous and non-ferrous metallic materials, such as welds and weld overlays, castings and forgings, valves and their components, pipe and fittings, machined parts, pressure vessels, plate material, and structural steel. Material verification is performed on components requiring certification to NACE MR0175/ISO 15156. Material verification is performed on both new and in-service equipment.

When performing material verification, the surface of the item must be accessible and subject to satisfactory cleaning and visual inspection. All analyzers have a margin of error that varies by element and activity of the radioactive source. The identification of small amounts of a specific element in an item can be difficult. Analyzers are limited to identifying only those alloys that are listed in the manufacturer's library for the analyzer. Material verification cannot be performed where the material temperature is in excess of approximately 200°F, unless specialized equipment and techniques are used. Carbon, sulphur and phosphorus cannot be identified with x-ray fluorescence (see Spectroscopy).

Test results are summarized in an inspection report. For NACE MR0175/ISO 15156 inspections the subject of the examination is die stamped with an IRISNDT identification number.